1. FATAL ACCIDENT IN A WASTEWATER TREATMENT PLANT

2. Introduction Recently a team arrived to carry out works in a decantation manhole at a wastewater treatment plant which was part of an accommodation camp. The task was to cut a length of existing pipe which was protruding into the manhole. This would enable a screening basket to be lowered into position. XXXXXX did not have control over the operations.

3. Description of the accident After a first period of work in the manhole, the two workers came back up to the surface to take a break. For reasons as yet undetermined, one of the workers went back to the manhole. After some time he was found by one of his colleagues lying at the bottom of the manhole, face down in the water. A colleague who found the worker was himself affected and in shock as he endeavoured to come to the man ’ s aid. Both were taken to hospital. The first person sadly died but the second was able to leave hospital after first aid.

4. Probable causes Absence of supervision? Ignorance of the risk? After the first job in the manhole, it appears that a tank truck emptied effluents into another manhole on the same network. No confirmation of this has been obtained, as the driver has not been found. It is possible toxic gas was given off during the emptying process and affected the two workers. The first person drowned after falling unconscious to the bottom of the manhole. The second was sufficiently overcome by the fumes to need to be rescued by others and transported to hospital.

5. Main Errors made The most basic safety measures were not complied with, namely: Before entering a manhole (or in fact any confined space where there could be toxic fumes or a lack of Oxygen), always perform a suitable gas detection test first. Throughout the job, personnel must be equipped with suitable personal gas detectors and alarms. A stand by man should always be stationed to raise the alarm.

6. Main Errors made Never leave anyone alone (or out of sight) at such a work location. If any one of these measures had effectively been implemented, a fatality would have been avoided. It is quite lucky that the second person (and perhaps the third and fourth...) were not overcome by fumes and also died. This is very common in this type of accident

7. Conclusion It is recommended that this information is widely disseminated and highlighted via Safety Meetings, etc. Unfortunately, operations on this type of facility are not always handled, with regard to safety, as carefully and methodically as on an industrial installation.

8. Pictures